Auerswald COMpact 5200 Advanced Information page 515

Indicatif régional sans zéro initial (p. ex. 5306...)
Your own external phone number, that is to be transferred, is sent to the
VoIP provider with the local area code, but without a leading zero (e.g.
5306).
Notes:
The PBX checks whether any of the specified phone numbers are to be
transferred, and if so which ones (Abonnés (Abo) > Propriétés >
Paramètres de ligne).
The transmitted phone number is automatically converted into the
selected format. If prefixes are necessary for converting your own phone
number, the prefixes set for the account are used (Réseaux publics >
Voix sur IP (VoIP) > Comptes > Configurer).
COMpact 5200/5200R/5500R - Firmware V7.2 - Advanced Information V04 07/2018
Settings – Réseaux publics
Voix sur IP (VoIP)
515